Entities such as pharmaceutical companies and university research labs commonly use vacuum filtration sterilization of biological fluids such as cell culture media and buffer solutions. This typically involves what are referred to as bottle-top filters such as the three-piece example shown in FIG. 1. A bottle-top filter device 10 includes an upper unfiltered sample reservoir 11 which is removable and disposable. The sample reservoir 11 includes a filter 12 which typically includes a polyethersulfone (PES) or cellulose-based membrane for sterilized filtering of the sample liquid. The upper rim of the sample reservoir 11 may receive a removable cover that protects the sample liquid from contamination. On the bottom is a filtrate storage bottle 13 for collecting the liquid filtrate, and in between is a vacuum collar 14 with a vacuum port for manual coupling of a vacuum source. Vacuum is applied downstream of the filter 12 to create a pressure differential which draws the sample liquid through the filter into the storage bottle 13. The upper rim of the storage bottle 13 may be adapted to receive a cap to close the container after filtering once it is disconnected from the vacuum collar 14. These components are normally sold pre-sterilized.
Such products and processes have various inherent challenges. For example potential spills are a significant concern. A spill can disrupt production for up to an entire day and require use of a sanitizing laminar hood. The need for manual attachment of the vacuum source to the vacuum port of the vacuum collar 14 may lead to problems with instability and risk of spillage.
When vacuum filtration systems are used with cell cultures, another concern is foaming. Filtrate pulled through the filter is apt to fall into the storage bottle and splash. Splashing can cause foaming of the filtered sample, a condition that can have detrimental effects on the cell cultures. Splashing and foaming can be caused by a variety of factors including the velocity at which the filtrate passes through the filter and the distance that it must fall before hitting the storage bottle or filtrate level within the storage bottle. The greater the velocity and distance, the more the filtrate is likely to foam.